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package com.baeldung.uuid;
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import org.junit.jupiter.api.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import java.lang.reflect.Method;
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import java.text.DecimalFormat;
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import java.util.HashSet;
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import java.util.Set;
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import static org.assertj.core.api.Assertions.assertThat;
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public class UUIDPositiveLongGeneratorUnitTest {
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private final static int NUMBER_OF_CHECKS = 1000000;
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private final static double COLLISION_THRESHOLD = 0.001;
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private final UUIDPositiveLongGenerator uuidLongGenerator = new UUIDPositiveLongGenerator();
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private final Logger logger = LoggerFactory.getLogger(UUIDPositiveLongGeneratorUnitTest.class);
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//private final UUIDPositiveLongGenerator uuidLongGenerator = new UUIDPositiveLongGenerator();
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Set<Long> uniqueValues = new HashSet<>();
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@Test
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void whenForeachGenerateLongValue_thenCollisionsCheck() throws Exception {
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printTableHeader();
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UUIDPositiveLongGenerator uuidLongGenerator = new UUIDPositiveLongGenerator();
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for (Method method : uuidLongGenerator.getClass().getDeclaredMethods()) {
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collisionCheck(method);
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}
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}
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private void printTableHeader() {
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logger.info(String.format("%-30s %-15s %-15s", "Approach(method name)", "collisions", "probability"));
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logger.info("-----------------------------------------------------------------------");
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}
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private void printOutput(String method, int collisionsCount, double collisionsProbability) {
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DecimalFormat decimalFormat = new DecimalFormat("#.#####");
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logger.info(String.format("%-30s %-15s %-15s", method, collisionsCount, decimalFormat.format(collisionsProbability)));
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}
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private void collisionCheck(Method method) throws Exception {
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Set<Long> uniqueValues = new HashSet<>();
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int collisions = 0;
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for (int i = 0; i < NUMBER_OF_CHECKS; i++) {
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long uniqueValue = (long) method.invoke(uuidLongGenerator);
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long uniqueValue;
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do uniqueValue = (long) method.invoke(uuidLongGenerator); while (!isUnique(uniqueValue));
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assertThat(uniqueValue).isPositive();
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if (!uniqueValues.add(uniqueValue)) {
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collisions++;
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}
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}
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double collisionsProbability = (double) collisions / NUMBER_OF_CHECKS;
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printOutput(method.getName(), collisions, collisionsProbability);
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assertThat(collisionsProbability).isLessThan(COLLISION_THRESHOLD);
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}
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private boolean isUnique(long value) {
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// Implement uniqueness checking logic, for example, by checking in the database
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return uniqueValues.add(value);
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}
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}
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